Methods and apparatuses for energetic neutral flux generation for processing a substrate

ABSTRACT

Apparatuses and methods for processing substrates are disclosed. A processing apparatus includes a chamber for generating a plasma therein, an electrode associated with the chamber, and a signal generator coupled to the electrode. The signal generator applies a DC pulse to the electrode with sufficient amplitude and sufficient duty cycle of an on-time and an off-time to cause events within the chamber. A plasma is generated from a gas in the chamber responsive to the amplitude of the DC pulse. Energetic ions are generated by accelerating ions of the plasma toward a substrate in the chamber in response to the amplitude of the DC pulse during the on-time. Some of the energetic ions are neutralized to energetic neutrals in response to the DC pulse during the off-time. Some of the energetic neutrals impact the substrate with sufficient energy to cause a chemical reaction on the substrate.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.12/862,359, filed Aug. 24, 2010, pending, the disclosure of which ishereby incorporated herein in its entirety by this reference.

TECHNICAL FIELD

Embodiments of the present disclosure relate generally to methods andapparatuses for treating a substrate, and more particularly, toperforming neutral beam activated chemical processing of the substrate.

BACKGROUND

Higher performance, lower cost, and greater density of integratedcircuits are ongoing goals of the computer industry. In processing theseintegrated circuits on semiconductor substrates, layers are oftendeposited on the substrate and subsequently some or all of the layersare removed. One process for material removal from a substrate is plasmaetching.

In plasma etching, plasma is utilized to assist etch processes byfacilitating an anisotropic removal of material along fine lines, withinvias, within contacts, and for other general patterning operations on asemiconductor substrate. Examples of such plasma assisted etchinginclude reactive ion etching (RIE), which is essentially an ionactivated chemical etching process.

In a plasma etching process reactive species are generated as a plasmafrom a bulk gas. The reactive species diffuse to a surface of a materialbeing etched and are adsorbed on the surface of the material beingetched. A chemical reaction occurs, which results in the formation of avolatile by-product, which is desorbed from the surface of the materialbeing etched and diffuses into the bulk gas, where it can be purged fromthe reaction chamber.

Many plasma reactors provide energy to a gas in the reactor chamber bycoupling Radio Frequency (RF) electric power into the chamber. The RFpower ionizes, dissociates, and excites molecules within the plasmabody. In particular, the RF power provides energy to free electrons inthe plasma body. Ionization may occur from an energized free electroncolliding with a gas molecule causing the gas molecule to ionize.Dissociation may occur from an energized free electron colliding with agas molecule, such as O₂, causing the molecule to break into smallermolecular or atomic fragments, such as atomic oxygen. Excitation occurswhen the collision, rather than breaking molecular bonds, transfersenergy to the molecule causing it to enter an excited state. Control ofthe relative amounts of ionization, dissociation, and excitation dependsupon a variety of factors, including the pressure and power density ofthe plasma. Due to ionization, the plasma body typically includessubstantially equal densities of negatively and positively chargedparticles.

Plasmas may be particularly useful for anisotropic etching of asemiconductor substrate. Anisotropic etching is etching that occursprimarily in one direction, whereas isotropic etching is etching thatoccurs in multiple directions. Anisotropic etching is desirable formanufacturing integrated circuit devices, because it can be used toproduce features with precisely located sidewalls that extendperpendicularly from the edges of a masking layer. This precision isimportant in devices that have feature sizes and spacing comparable tothe depth of the etch.

To accomplish an anisotropic plasma etch, a semiconductor substrate suchas a wafer may be placed in a plasma reactor such that a plasma forms inan electric field perpendicular to the substrate surface. This electricfield accelerates ions perpendicularly toward the substrate surface foretching. One conventional approach to anisotropic plasma etching usesparallel planar electrodes. Often, the lower electrode acts as apedestal for a wafer. RF power is applied to the electrodes to produce aplasma and accelerate ions toward the substrate surface.

The crystalline silicon or thin insulating layers of some modernintegrated circuit designs may be damaged by high energy ionbombardment, so it may be necessary to decrease the RF power applied tothe electrodes for lower ion energy etch processes. Decreasing the RFpower, however, will reduce the ion density in the plasma. Decreased iondensity usually decreases the etch rate.

Inductively coupled plasma reactors have been used with an RF couplingmechanisms to generate the plasma and control the ion density and ionbombardment energy. Power is applied to an induction coil surroundingthe reactor chamber to inductively couple power into the chamber toproduce the plasma. The inductively coupled power accelerates electronscircumferentially within the plasma. As a result, the charged particlesgenerally do not accelerate in any specific direction. To move ionstoward a substrate some type of bias is typically applied between thesubstrate and the plasma. In other words, a separate source of power maybe needed and applied to a substrate support to accelerate ions towardthe substrate for etching. A relatively high level of power may beapplied to the induction coil to provide a plasma with a high iondensity, and a relatively low level of power may be applied to thesubstrate support to control the energy of ions bombarding the substratesurface. As a result, a relatively high rate of etching may be achievedwith relatively low energy ion bombardment.

While low energy ion bombardment may reduce damage to sensitive layersof the integrated circuit, other problems may be encountered thatinterfere with the anisotropic nature of the etch. In particular, lowenergy ions may be deflected by charges that accumulate on the substrateor mask surface during etching causing a charge buildup.

This charge buildup may result from the relatively isotropic motion ofelectrons in the plasma as opposed to the anisotropic motion of theions. The normal thermal energy of the plasma causes the electrons tohave high velocities because of their low mass. These high velocityelectrons collide with molecules and ions and may be deflected in avariety of directions, including toward the substrate surface. While thenegative bias on the substrate tends to repel electrons, the highvelocity of some electrons overcomes this negative bias. The electronsare deflected in a variety of directions and have a relatively isotropicmotion. As a result, electrons deflected toward the substrate surfacetend to accumulate on elevated surfaces of the substrate or mask layer,rather than penetrating to the depths of narrow substrate features.

Ions, on the other hand, have a large mass relative to electrons, do nothave high random velocities, and are directed toward the substrate in aperpendicular direction. This anisotropic acceleration allows ions topenetrate to the depths of narrow substrate features more readily thanelectrons.

As a result, negatively charged electrons tend to accumulate on theupper surfaces of the substrate or mask layer, while positively chargedions tend to accumulate in the recessed regions of the substrate thatare being etched. These accumulated charges may form small electricfields, often referred to as “micro fields,”' near features on thesurface of the substrate. While these small electric fields may havelittle effect on high energy ions, they may deflect low energy ions usedin low energy etch processes for small integrated circuit features. Thenegative charge on the substrate or mask surface tends to attractpositively charged ions, while the positive charge in recessed regionstends to repel these ions. As a result, low energy ions falling intorecessed regions between features may be deflected into featuresidewalls, thereby undercutting the mask layer. This undercutting candegrade the anisotropic etch process and inhibit the formation ofwell-defined features with vertical sidewalls.

Because of these issues, and others, neutral beam etching processes havebeen proposed. In a neutral beam process, the ions are acceleratedtoward the substrate, but they then pass through a variety of proposedmechanisms to neutralize the ions by supplying electrons to the ions.The neutralized ions then strike the surface of the substrate with anamount of kinetic energy related to the mass and velocity of theneutralized ions. That kinetic energy is enough to cause a chemicalreaction on the surface of the substrate. In other words, the chemicalprocess, such as an etching process, at the substrate is activated bythe kinetic energy of the incident neutral species.

These previously proposed neutralizing structures take different forms.As an example, one proposal includes a deflection plate that deflectsthe ions as they move toward the substrate by a small angle in onedirection then another deflection plate deflects the ions back to aperpendicular direction relative to the substrate. These deflectionplates are negatively charged such that the ions can readily pick upelectrons and neutralize as they strike the plates and before theystrike the substrate.

In another example of a previous proposal, one or more grids aredisposed between a region where the plasma exists and the substrate.These grids may be configured to emit electrons such that as the ionstravel through the grids and toward the substrate these emittedelectrons are available for recombination with the ions to createneutral species for impact with the substrate.

However, these previously proposed neutral beam etching apparatusesrequire additional elements to be added to the reaction chamber toneutralize the ions. These additional elements add complexity and costto the chamber as well as new elements that must be maintained.Moreover, as semiconductor wafers become very large, such as 300millimeter wafers and above, these additional elements generally mustspan an area even larger than the wafer which may introduce structuralproblems with how to build the neutralizing structures without anyphysical deformation across the large area.

The inventor has appreciated that for the reasons stated above, and forother reasons, there is a need in the art for alternative and simplifiedstructures and processes for generating neutral beam flux for processingsubstrates.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, which illustrate embodiments of the invention:

FIG. 1A is a simplified diagram of a processing chamber for generatingplasma and energetic neutrals from the plasma;

FIG. 1B depicts another embodiment of an upper portion of the processingchamber of FIG. 1A;

FIGS. 2A-2C are timing diagrams illustrating waveforms representingpulsed direct current (DC) signals that may be used in variousembodiments discussed herein;

FIGS. 3A-3C show generation of energetic neutrals from a plasma atvarious points in time during substrate processing;

FIG. 4 is a flow diagram illustrating some of the acts performed duringgeneration of energetic neutrals from a plasma;

FIGS. 5A-5C show generation of energetic reactive neutrals from a plasmaat various points in time during substrate processing; and

FIGS. 6A-6D show generation of energetic inert neutrals from a plasma atvarious points in time during substrate processing.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings which form a part hereof, and in which is shown byway of illustration specific embodiments in which the invention may bepracticed. These embodiments are described in sufficient detail toenable those of ordinary skill in the art to practice the invention, andit is to be understood that other embodiments may be utilized, and thatprocess, chemical, structural, logical, and electrical changes may bemade within the scope of the present invention.

The terms “wafer” and “substrate” are to be understood as asemiconductor-based material including silicon, silicon-on-insulator(SOI) or silicon-on-sapphire (SOS) technology, thin film transistor(TFT) technology, doped and undoped semiconductors, epitaxial layers ofsilicon supported by a base semiconductor foundation, and othersemiconductor structures. Furthermore, when reference is made to a“wafer” or “substrate” in the following description, previous processsteps may have been utilized to form regions or junctions in or over thebase semiconductor structure or foundation. The semiconductor need notbe silicon-based, but may be based on silicon-germanium,silicon-on-insulator, silicon-on-sapphire, germanium, or galliumarsenide, among others. In addition, directional references, e.g.,upper, lower, top, bottom and sides, are relative to one another andneed not refer to an absolute direction.

Moreover, some embodiments may be configured for use in the formation ofmasks for semiconductor devices. As a result, a substrate may alsoinclude transparent substrates (e.g., quartz and glass) suitable forbearing photolithography masks thereon.

It should be understood that any reference to an element herein using adesignation such as “first,” “second,” and so forth does not limit thequantity or order of those elements, unless such limitation isexplicitly stated. Rather, these designations may be used herein as aconvenient method of distinguishing between two or more elements orinstances of an element. Thus, a reference to first and second elementsdoes not mean that only two elements may be employed there or that thefirst element must precede the second element in some manner. Also,unless stated otherwise a set of elements may comprise one or moreelements.

Also, it is noted that the embodiments may be described in terms of aprocess that is depicted as a flowchart, a flow diagram, a structurediagram, or a block diagram. Although a flowchart may describeoperational acts as a sequential process, many of these acts can beperformed in another sequence, in parallel, or substantiallyconcurrently. In addition, the order of the acts may be re-arranged.

For ease of following the description, for the most part element numberidentifiers begin with the number of the drawing on which the elementsare introduced or most fully discussed. Thus, for example, elementidentifiers on a FIG. 1 will be mostly in the numerical format I xx andelements on a FIG. 4 will be mostly in the numerical format 4xx.

Embodiments discussed herein provide simplified structures and processesfor generating neutral beam flux for processing substrates by usingDirect Current (DC) pulses to generate plasmas and convert ions withinthe plasma to energetic neutral species directed toward a substrate.

FIG. 1A is a simplified diagram of a processing apparatus 100 forgenerating plasma and energetic neutrals from the plasma. A processingchamber 110 includes an electrode 140 disposed therein. This electrode140 may be substantially circular and disposed opposite a substrateholder 150. A substrate 310 is shown disposed on the substrate holder150. One or more inlet ports 120 may be configured to introduce a gas125 into the processing chamber 110 and pressurize or depressurize theprocessing chamber 110 to a suitable pressure as discussed below. One ormore exhaust ports 130 may be configured to purge the processing chamber110 of effluent gasses 135 after some processing steps.

The substrate holder 150 may include a temperature adjuster 152controlled by a signal generator 180 or other type of controller (notshown). Details of temperature adjustment are discussed more fullybelow. The signal generator 180 may also be configured to apply asubstrate signal 155 to the substrate holder 150 and the substrate 310thereon to bias the substrate holder 150 and substrate 310 to a desiredvoltage as discussed below.

The signal generator 180 may also apply a chamber bias signal 115coupled to the processing chamber 110 and for setting portions or all ofthe interior walls to a chamber bias voltage. In many embodiments, thechamber bias signal 115 would be set to a ground voltage. The chamberbias signal 115 may also be referred to herein as a first DC signal 115.

The signal generator 180 may also apply an electrode signal 145 to theelectrode 140. The electrode signal 145 may also be referred to hereinas a pulsed DC signal 145 and a second DC signal 145. The pulsed DCsignal 145, when driven with a sufficiently high voltage, will cause aplasma 190 to form from the gas 125 disposed in the processing chamber110.

FIG. 1B depicts another embodiment of an upper portion of the processingchamber 110 of FIG. 1A. In the FIG. 1B embodiment, the electrode 140Adriven by the pulsed DC signal 145 is disposed outside the processingchamber 110 and near a dielectric window 142 formed in an upper wall ofthe processing chamber 110. In this configuration, the electrode 140Amay capacitvely couple through the dielectric window 142 with theinterior of the processing chamber 110 to develop voltage potential inthe interior of the processing chamber 110 sufficient for generating theplasma 190.

FIGS. 2A-2C are timing diagrams illustrating waveforms (210, 220, and230) representing pulsed direct current (DC) signals that may be used invarious embodiments discussed herein. Referring to FIG. 1A as well asFIGS. 2A-2C, waveform 210 illustrates a series of DC pulses that may beapplied to the electrode signal 145. Waveform 220 illustrates a voltagepotential that will develop within the processing chamber 110 as aresult of the pulsed DC signal 145 applied to the electrode 140.Waveform 230 illustrates a possible bias that may be applied in someembodiments to the substrate 310 through the substrate signal 155.Arrows near the rising edge and falling edge of Waveform 230 illustratethat the pulse initiation and duration may be adjusted relative towaveform 210 as is explained more fully below. In general, the biasshown by waveform 230 indicates that the substrate signal 155 would havea negative DC pulse (i.e., from Vlow to Vsub) relative to the positiveDC pulse on the electrode signal 145 shown by waveform 210.

The parameter Vlow illustrates a beginning voltage for the pulsed DCsignals (waveforms 210, 220, and 230). In many embodiments, this Vlowparameter would be set to a DC ground. The Vhi parameter indicates ahigh voltage applied to the electrode 140. At a plasma voltage,designated Vp, the voltage will be high enough to generate a plasma 190from the gas 125 in the chamber and cause some of the molecules in thegas 125 to ionize creating free electrons and ions from the gas 125.After a first time period 212 (also referred to herein as an on-time212), the voltage is returned to Vlow for a second time period 214 (alsoreferred to herein as an off-time 214). These pulses may be repeated anumber of times to create periodic DC pulses as explained more fullybelow. The amplitude between Vhi and Vlow may be referred to herein as afirst voltage difference 216.

In some embodiments, once the plasma 190 has formed, the voltage onwaveform 210 may be adjusted up or down (illustrated as down to a secondvoltage difference 218 on FIG. 2A and 228 on FIG. 2B). This adjustmentmay be done to promote or reduce the voltage potential that acceleratesions toward the substrate 310 as explained more fully below.

Pulse durations, amplitude of the voltage (i.e., the difference betweenVhi and Vlow), and number of pulses may vary greatly depending on thetype of processing to be performed. As non-limiting examples, the Vhivoltage may be in the 100 s of volts and possibly up to kilovolts. Asnon-limiting examples, pulse duration may be in the second tomillisecond range and possible down to microseconds.

FIGS. 3A-3C show generation of energetic neutrals 354 from a plasma 190at various points in time during substrate processing.

FIG. 4 is a flow diagram illustrating some of the acts performed duringgeneration of energetic neutrals 354 from a plasma 190. FIGS. 4 and3A-3C are discussed together to illustrate an energetic neutralgeneration process 400. In addition, reference will be made to FIGS. 1Aand 2A-2C, when discussing the processing apparatus 100 and waveforms.

At operation 402, a gas is introduced into the processing chamber 110.The gas may be many different species of inert gasses as well as manydifferent species of reactive gasses. More details of the types ofgasses are discussed below with reference to FIGS. 5A-5C and FIGS.6A-6D.

At operation 404, a voltage is applied to the electrode 140. Atoperation 406, the voltage on the electrode, and voltage potentialwithin the processing chamber 110, is high enough to ionize the gas intoelectrons 340 and ions 350 and form the plasma 190 above the substrate310, as shown in FIG. 3A. In some embodiments, a material 320 to beprocessed (e.g., etched) may be disposed on the substrate 310. In otherembodiments, the substrate 310 itself may be the material to beprocessed.

At operation 408, the voltage potential on the electrode 140 ismaintained to maintain the plasma and to accelerate the ions toward thesubstrate as energetic ions 352, as shown in FIG. 3B. The high voltageon the electrode 140 will repel the positively charged ions away fromthe electrode and toward the substrate. As mentioned earlier, thevoltage on the electrode 140 may be adjusted up or down to a secondvoltage difference 218 for a portion of the pulse to respectivelyenhance or impede the acceleration of ions toward the substrate 310.

At operation 410, the voltage on the electrode is reduced to Vlow, whichcauses the plasma to collapse. The initial pulse potential causes anionization event that triggers free electrons that have the ability tocause additional ionization events, which generates the plasma. Removalof the pulse potential collapses (i.e., self neutralizes) the plasmabecause there is no driving potential to cause electron acceleration tomaintain the plasma.

Removal of the pulse potential also enables the energetic ions 352 torecombine with free electrons 340 in the chamber to create energeticneutrals 354, as shown in FIG. 3C. There is a natural tendency for thecharged energetic ions 352 to interact with electrons 340 and neutralizethe energetic ions 352, which are then referred to herein as energeticneutrals 354.

Therefore, during the time the electrode is off (or at the Vlowpotential) the positive energetic ions 352 have a velocity directed awayfrom the electrode 140, the energetic ions 352 will become neutralizedbut will retain their thermal velocity toward the substrate 310 tobecome energized neutral species.

The energetic ions 352 have a momentum towards the substrate 310,whereas the electrons 340 may be moving in any random direction.However, because the mass of the energetic ions 352 is so much higherthat the electrons 340, the electrons 340 will move toward the energeticions 352 and when they combine to form the energetic neutrals 354 thedirectional momentum of the energetic neutrals 354 is not modifiedsignificantly.

“Energized” or “energetic” as used herein means that the ions orneutrals have kinetic energy due to their momentum, rather than havingany specific type of charge. Ions have a positive charge and neutralshave a neutral charge.

While not illustrated in FIG. 4, it should be understood that theoff-time 214, as shown in FIG. 2A, may be adjusted to allow sufficienttime for the neutralization of most, if not all, of the energetic ions352.

At operation block 412, the energetic neutrals 354 bombard (alsoreferred to herein as impact) the surface of the substrate 310 or thematerial 320 disposed on the substrate 310. When the energetic neutrals354 hit the surface, they don't have an electrical charge, which maypromote reactions with the material 320. However, the energetic neutrals354 do have kinetic energy due to their momentum. This energy may besufficient to promote or cause chemical reactions in the material 320.As a non-limiting example, this chemical reaction may cause an etchingof the material 320.

At decision block 414, a determination is made if a sufficient chemicalreaction has occurred with the material 320, substrate 310, arecombination thereof. This determination may be made from measurements ofthe chemical reaction or may be determined as a predetermined timeperiod or number of pulses that would cause the desired amount ofchemical reaction. If sufficient reaction has not occurred, the processloops back to operation block 404 to begin a new DC pulse. If sufficientreaction has occurred, gas in the processing chamber 110 may be purgedat operation block 416 to prepare for additional processing steps.

Thus, the process 400 may continue the flux of energetic neutrals 354for a predetermined time period, such as, for example, a few seconds toget enough bombardment by energetic neutrals 354 to obtain the desiredreactions.

Energetic species bombarding a substrate 310 with enough energy maycause physical sputtering, which may cause undesired damage to thesubstrate. Therefore, embodiments of the present invention may limit oreliminate physical sputtering while still allowing chemical sputtering(i.e., the chemical reactions). In other words, the chemical reactionwill appear more like reactive ion etching even though neutrals areused, rather than ions, and physical sputtering can be reduced bylimiting the energy of the energetic neutrals 354.

Embodiments of the present invention may be particularly useful forAtomic Layer Etching (ALE) because the energetic neutrals can be wellcontrolled to remove a single atomic layer of the material 320 or thesubstrate 210.

The energy of the energetic neutrals 354 may be controlled as discussedabove based on the amplitude of the first voltage difference 216 and thesecond voltage difference 218. In addition, some embodiment may apply abias to the substrate holder 150 and substrate 310 to modify themomentum of the energetic neutrals 354. As shown in FIG. 2C and FIG. 1A,the substrate signal 155 (represented by waveform 230) may include anegative voltage potential (Vsub) relative to Vlow to attract theenergetic neutrals 354 toward the substrate 310. Moreover, the edges ofthe DC pulse on the substrate signal 155 may be moved relative to theedges on the electrode signal 145 (represented by waveform 210). As anon-limiting example, the falling edge of the substrate signal 155 maybe moved to the right relative to the rising edge of the electrodesignal 145 such that the attraction to the substrate 310 does not beginuntil after the plasma 190 has formed. As another non-limiting examplethe rising edge of the substrate signal 155 may be moved to the rightrelative to the falling edge of the electrode signal 145 to continueacceleration of the energetic ions 352 toward the substrate 310 evenafter the acceleration due to the positive potential on the electrodesignal 145 is gone.

As a result, there are many mechanisms for controlling the energy of theenergetic neutrals 354 when they impact the substrate 310. Thesemechanisms include the amplitude of the first voltage difference 216,the amplitude of the second voltage difference 218, the on-time 212 ofthe electrode signal 145, the off-time 214 of the electrode signal 145and in some embodiments, the amplitude and relative timing of thesubstrate signal 155.

FIGS. 5A-5C show generation of energetic reactive neutrals 554 from aplasma 190 at various points in time during substrate processing.Chlorine is used as an example of a reactive gas in the processing shownin FIGS. 5A-5C. However, many other gasses, such as, for example,fluorine and other reactive species may be used depending on the type ofchemical reaction desired with the substrate 310, material 320 on thesubstrate 310, or combination thereof. Chlorine gas is introduced intothe processing chamber 110 and ionized to create chlorine ions 550 andelectrons 540 in a plasma 190, as shown in FIG. 5A. The chlorine ionsare accelerated toward the substrate 310 to create energetic chlorineions 552, as shown in FIG. 5B. This process is similar to that discussedabove with respect to generic energetic ions 352 and need not berepeated.

The energetic chlorine ions 552 are neutralized to energetic chlorineneutrals 554, as shown in FIG. 5C. Again, this process is similar tothat discussed above with respect to generic energetic neutrals 354 andneed not be repeated. In the example of FIGS. 5A-5C, the energeticchlorine neutrals 554 impact the substrate 310 and silicon thereon tocause a chemical reaction, generate silicon tetrachloride 556, and etcha portion of the silicon. The silicon tetrachloride 556 can be purgedfrom the processing chamber 110 after the desired reactions havecompleted. This process is similar to a reactive ion etch process exceptthat reactive neutrals are used, rather than ions, and the kineticenergy of the reactive neutrals supplies enough energy for the reactionbetween the silicon and the energetic chlorine neutrals 554 to occur.

FIGS. 6A-6D show generation of energetic inert neutrals 654 from aplasma 190 at various points in time during substrate processing. InFIGS. 6A and 6B, chlorine gas 660 is introduced to the processingchamber 110 and chemisorbed as chlorine 662 on the substrate 310 throughany suitable process, such as, for example, atomic layer deposition orbulk deposition. Excess chlorine gas 660 may be purged from theprocessing chamber 110, by any suitable means, such as, for example, anargon purge.

FIGS. 6C and 6D illustrate the pulsed DC plasma process as discussedabove with reference to FIGS. 3A-3C, but with energetic inert neutrals654 rather than generic energetic neutrals 354. For brevity, the processacts associate with FIG. 3A are not shown and the process acts of FIGS.6C and 6D are similar to those of FIGS. 3B and 3C, respectively. Argonis used as an example of an inert gas in the processing shown in FIGS.6C and 6D. However, many other gasses, such as, for example, nitrogen,neon and other inert species may be used to cause a chemical reaction onthe substrate 310, material 320 on the substrate 310, or combinationthereof.

Argon gas is introduced into the processing chamber 110 and ionized tocreate argon ions (not shown) and electrons 640 in a plasma 190. Theargon ions are accelerated toward the substrate 310 to create energeticargon ions 652, as shown in FIG. 6C. This process is similar to thatdiscussed above with respect to generic energetic ions 352 and need notbe repeated.

The energetic argon ions 652 are neutralized to energetic argon neutrals654, as shown in FIG. 6D. Again, this process is similar to thatdiscussed above with respect to generic energetic neutrals 354 and neednot be repeated. In the example of FIGS. 6A-6D, the energetic argonneutrals 654 impact the substrate 310 of silicon and the chlorine 662disposed thereon. The energy of the impact is sufficient to cause thechlorine to break up and become reactive upon impact by the energeticargon neutrals 654 causing a chemical reaction between the silicon andchlorine to generate silicon tetrachloride 556 and etch a portion of thesilicon. The silicon tetrachloride 556 can be purged from the processingchamber 110 after the desired reactions have completed. With thisprocess, an atomic layer etch of the silicon may be accomplished.

The example discussed above with respect to FIGS. 6A-6D illustrateschlorine 662 being chemisorbed onto the substrate 310. However, aspecies also may be physisorbed on the substrate 310. Thus, in FIGS. 6Aand 6B, with the proper chamber parameters and substrate temperature,the chlorine 662, or other suitable material (e.g., BCL₃ and HBr), maybe physisorbed onto silicon by any suitable process such as, forexample, atomic layer deposition or bulk deposition.

Then, in the example of FIGS. 6A-6D, the energetic argon neutrals 654impact the substrate 310 of silicon and the chlorine 662 disposedthereon. The energy of the impact is sufficient to cause a chemicalreaction between the silicon and physisorbed chlorine to generatesilicon tetrachloride 656 and etch a portion of the silicon. The silicontetrachloride 656 can be purged from the processing chamber 110 afterthe desired reactions have completed. With this process, an atomic layeretch of the silicon may be accomplished. Of course, other substratematerials may be used and other physisorbed species may be used to causea chemical reaction therebetween when energy is supplied by the impactof the energetic neutrals 654.

Examples have been discussed using specific substrates, materials, andchemical reactions to describe embodiments of the present invention.However, many other substrates, materials, and energetic neutral speciesmay be used. As non-limiting examples, silicon, silicon dioxide, hafniumoxide, silicon nitride, and metals such as copper, may be used as thesubstrate 310 or material 320 thereon.

Pressure in the processing chamber 110 may be set at a broad range ofpressures depending on the type of gas to be ionized, the voltage on thepulsed DC signal 145, and other factors. The pressure may be readilydetermined by a person skilled in the art of plasma generation with DCsignals. As non-limiting examples, the pressure may be in the range ofmillitorrs to torrs. As a low-end non-limiting example, the pressure maybe near about 10 millitorrs. In some, embodiments, the pressure may beas high as near atmospheric pressure.

Returning to FIG. 1A, it may be useful to modify the temperature of thesubstrate 310 to promote or suppress the chemical reactions. As aresult, the processing apparatus 100 may include the temperatureadjuster 152. The temperature adjuster 152, under control of the signalgenerator 180 or other controller (not shown), may be configured toadjust and control the temperature of the substrate 310. The temperatureadjuster 152 may include temperature control elements, such as a coolingsystem including a re-circulating coolant flow that receives heat fromthe substrate holder 150 and transfers heat to a heat exchanger system(not shown), or when heating, transfers heat from the heat exchangersystem. Additionally, the temperature control elements can includeheating/cooling elements, such as resistive heating elements, orthermoelectric heaters/coolers, which can be included in the substrateholder 150.

The signal generator 180 may be a dedicated device configured forgenerating the various signals defined above. The signal generator 180may also be a special purpose controller, a general purpose controller,a special purpose processor, or a general purpose microprocessor withaccompanying devices such as voltage control devices, analog-to-digitalconverters, digital-to-analog converters, and memories. The memories mayinclude volatile storage such as Dynamic Random Access Memory (DRAM) andStatic Random Access Memory (SRAM) as well as non-volatile memory andstorage such as Erasable Programmable Read-Only Memory (EPROM), Flashmemory, magnetic storage devices, and optical storage devices.

CONCLUSION

Embodiments discussed herein provide simplified structures and processesfor generating neutral beam flux for processing substrates.

In some embodiments, a method of treating a substrate includes forming aplasma in a processing chamber. Ions of the plasma are accelerated tobecome energetic ions moving toward a substrate disposed in theprocessing chamber. At least some of the energetic ions are neutralizedto generate energetic neutrals moving toward the substrate by collapsingthe plasma and at least some of the energetic neutrals impact thesubstrate.

In other embodiments, a method of treating a substrate includes applyinga first DC signal to an interior portion of a processing chamber. Asecond DC signal is applied to an electrode associated with theprocessing chamber with a first voltage difference between the second DCsignal and the first DC signal sufficient to establish a plasma withinthe processing chamber. A second voltage difference is maintainedbetween the second DC signal and the first DC signal for a first timeperiod sufficient to accelerate ions of the plasma toward the substrateas energetic ions. Subsequently, the voltage difference between thefirst DC signal and the second DC signal is reduced for a second timeperiod and to a magnitude sufficient to neutralize at least some of theenergetic ions to energetic neutrals moving toward the substrate. Insome embodiments, the first voltage difference and the second voltagedifference may be equal.

In other embodiments, a method of treating a substrate includes forminga reactive film on a surface of a substrate disposed in a processingchamber from a reactive gas introduced into the processing chamber. Aplasma is formed from an inert gas introduced in the processing chamber.Ions of the plasma are accelerated to become energetic inert ions movingtoward the substrate. At least some of the energetic inert ions areneutralized by collapsing the plasma to generate energetic inertneutrals moving toward the substrate and the at least some of theenergetic inert neutrals impact the substrate.

In yet other embodiments, a processing apparatus includes a processingchamber for generating a plasma therein, an electrode associated withthe processing chamber, and a signal generator operably coupled to theelectrode. The signal generator is configured for applying a DC pulse tothe electrode. The DC pulse has sufficient amplitude and sufficient dutycycle of an on-time and an off-time to cause events within theprocessing chamber. A plasma is generated from a gas disposed in theprocessing chamber responsive to the amplitude of the DC pulse.Energetic ions are generated by accelerating ions of the plasma toward asubstrate disposed in the processing chamber in response to theamplitude of the DC pulse during the on-time, and at least some of theenergetic ions are neutralized to energetic neutrals in response to theDC pulse during the off-time.

In still other embodiments, a method of treating a substrate includesforming a physisorbed inert species on a surface of a substrate disposedin a processing chamber. A plasma is formed from an inert gas introducedin the processing chamber. Ions of the plasma are accelerated to becomeenergetic inert ions moving toward the substrate. At least some of theenergetic inert ions are neutralized by collapsing the plasma togenerate energetic inert neutrals moving toward the substrate and the atleast some of the energetic inert neutrals impact the substrate.

Although the present invention has been described with reference toparticular embodiments, the present invention is not limited to thesedescribed embodiments. Rather, the present invention is limited only bythe appended claims and their legal equivalents.

1. A method of treating a substrate, comprising: applying a first DCsignal to an interior portion of a processing chamber; applying a secondDC signal to an electrode associated with the processing chamber with afirst voltage difference between the second DC signal and the first DCsignal sufficient to establish a plasma within the processing chamber;maintaining a second voltage difference between the second DC signal andthe first DC signal for a first time period sufficient to accelerateions of the plasma toward the substrate as energetic ions; and after themaintaining, reducing the second voltage difference between the first DCsignal and the second DC signal for a second time period and to amagnitude sufficient to neutralize at least some of the energetic ionsto energetic neutrals moving toward the substrate.
 2. The method ofclaim 1, wherein the first voltage difference and the second voltagedifference are the same.
 3. The method of claim 1, wherein applying thefirst DC signal comprises applying a ground as the first DC signal. 4.The method of claim 1, further comprising applying a third DC voltage tothe substrate at a voltage potential sufficient to assist in theaccelerating the ions toward the substrate by attracting the ions towardthe substrate.
 5. The method of claim 1, further comprising lowering atemperature of the substrate below an ambient temperature of theprocessing chamber.
 6. The method of claim 1, further comprising raisinga temperature of the substrate above an ambient temperature of theprocessing chamber.
 7. The method of claim 1, wherein the applying thesecond DC signal, the maintaining, and the reducing occur sequentiallyto form a pulsed DC signal on the second DC signal relative to the firstDC signal.
 8. The method of claim 7, wherein the pulsed DC signal isrepeated to form a sequence of periodic DC pulses for a predeterminedtime period.
 9. A processing apparatus, comprising: a processing chamberfor generating a plasma therein; an electrode associated with theprocessing chamber; and a signal generator operably coupled to theelectrode and configured for applying a DC pulse to the electrode withsufficient amplitude and sufficient duty cycle of an on-time and anoff-time to: generate the plasma from a gas disposed in the processingchamber responsive to the amplitude of the DC pulse; generate energeticions by accelerating ions of the plasma toward a substrate disposed inthe processing chamber responsive to the amplitude of the DC pulseduring the on-time; and neutralize at least some of the energetic ionsto energetic neutrals responsive to the DC pulse during the off-time.10. The processing apparatus of claim 9, wherein the signal generator isfurther configured to cause at least some of the energetic neutrals toimpact the substrate with sufficient energy to cause an atomic layeretch of a material on a surface of the substrate by causing a chemicalreaction with the material.
 11. The processing apparatus of claim 10,wherein the signal generator is further configured to repeat the DCpulse until the chemical reaction is sufficient to remove apredetermined amount of the material, a predetermined time period haselapsed, or a combination thereof.
 12. The processing apparatus of claim9, further comprising a temperature adjuster operably coupled to asubstrate holder bearing the substrate, the temperature adjusterconfigured to adjust a temperature of the substrate higher or lower thanan ambient temperature in the processing chamber.
 13. The processingapparatus of claim 9, wherein at least one interior surface of theprocessing chamber is operably coupled to a ground.
 14. The processingapparatus of claim 9, wherein the signal generator is further configuredto generate a substrate signal operably coupled to the substrate andconfigured to assist the accelerating the ions of the plasma byattracting the energetic ions toward the substrate during at least aportion of the on-time, at least a portion of the off-time, or acombination thereof.
 15. The processing apparatus of claim 9, furthercomprising an inlet port configured for introducing the gas to theprocessing chamber, wherein the gas is an inert gas for generatingenergetic inert neutrals.
 16. The processing apparatus of claim 9,further comprising an inlet port configured for introducing the gas tothe processing chamber, wherein the gas is a reactive gas for generatingenergetic reactive neutrals.
 17. The processing apparatus of claim 9,wherein the electrode is disposed within the processing chamber,substantially parallel to the substrate, and opposing the substrate. 18.The processing apparatus of claim 9, further comprising a dielectricwindow through a wall of the chamber and wherein the electrode isdisposed adjacent the dielectric window, external from the processingchamber, substantially parallel to the substrate, and opposing thesubstrate.
 19. A processing apparatus, comprising: a processing chamber;an electrode associated with the processing chamber; and a signalgenerator operably coupled to the electrode and configured for: applyinga DC voltage to the electrode with sufficient amplitude to cause aplasma to form from a gas disposed in the processing chamber;maintaining the DC voltage on the electrode for a first durationsufficient to accelerate ions of the plasma to become energetic ionsmoving toward a substrate disposed in the processing chamber; andremoving the DC voltage from the electrode for a second durationsufficient to: neutralize at least some of the energetic ions bycombining with electrons to generate energetic neutrals moving towardthe substrate; and retain a kinetic energy of the energetic neutralstoward the substrate.
 20. The processing apparatus of claim 19, whereinthe signal generator is further configured to sequentially repeatapplying the DC voltage, maintaining the DC voltage, and removing the DCvoltage a number of times sufficient to remove a predetermined amount ofmaterial from the substrate, for a predetermined time period, or acombination thereof.